Hydraulic tracing apparatus



E. J. HlRvoNEN 2,882,777

HYDRAULIC TRACING APPARATUS a sheets-shet 1 Nm. ow.

//^m\ u8. o

INVENTOR- lo J.H1RvoNEN ATTORNEY #In I|11|! `l i [W p w p e@ M l w April 21, 1959 Filed Nov. 3, 1955 mu "mlm /||.H. H ON NM l.\\ L I April 21, 1959 E. J. HlRvoNEN y HYDRAULIC TRACING APPARATUS 8 Sheets-Sheet 2 INVENTOR ERIG J. HIRVONEN Filed NOV. 3, 1955 ATTORNEY April 21, 1959 E. J. HlRvoNEN HYDRAULIC TRACING APPARATUS 8. Sheets-Sheet 5 Filed Nov. 3, 1955 mg A \\\wvu I'I ll l I| l I INVENTOR`V ATTORNEY Ill //l/l/I-//////v/// ERIC J HIRVONEN M I l *I ||Il iw@ A l A April 2l, 1959 E. J. HlRvoNEN 2,882,777

HYDRAULIC TRACING APPARATUS Filed Nov. s, 1955 sheets-sheet 4 INVENTOR |04 ERIC J. HIRVONEN ATTORNEY @im Nimm., "Mmm, "Mmmm www.. I 28 lo `/v all /l'rnm G E. J. HIRVONEN HYDRAULIC TRACING APPARATUS April 2l, 1959 Filed NOV. 5, 1955 8 Sheets-Sheet 5 R om TN No M E VVW R N l |.H J w R f Y E N R O T T A April 21, 1959 E.- J. HIRVONEN HYDRAULIC TRACING APPARATUS 8 Sheets-Sheet 6 Filed NOV. 3, 1955 @SAUNA "IHUHMA O ll IHM

INVENTOR FIGIG ERIC J.H|RVONEN ATTORNEY April 2l, 1959 'l E. JfHlRvoNr-:N

HYDRAULIC TRACING APPARATUS Filed NOV. 3, 1955 8 sheets-sheet 7 ATTORNEY April 21, 1959 E. J. HIRVONEN 2,882,777

HYDRAULIC TRACINGYAPPARATUS Filed Nov.` 5, 1955 sheets-sheet 8 lala nge INVENTOR ERIC J. HIRVONEN ATTORNEY United States Patent HYDRAULIC TRACING APPARATUS Application November 3, 1955, Serial No. 544,760

Claims. (Cl. 82-14) This invention relates to a new and improved hydraulic tracing apparatus, the principal object of which resides in the provision of a completely self-contained unit for attachment to a conventional machine tool such as an engine lathe, said unit being quickly and easily applied to the lathe or other machine tool and being adapted to be removed therefrom for operation of the lathe or machine tool in its customary manner; the provision of a self-contained tracing unit as above described including the tracing element, the copying tool, and fluid pressure means for moving the tool in accordance with the tracer element, said uid system being completely incorporated in a selfcontained unit which includes a prime mover such as an electric motor for operating the same, it being necessary only to mount the unit on the cross slide of a lathe, etc., and to plug the motor into a convenient electric outlet in order to convert the lathe into a copying lathe; and the provision of a hydraulic system for the unitary tracing apparatus as aforesaid in which the elec* tric motor for the pump may be extremely small as compared with prior art devices, being in the nature of onesixth horsepower or up to one-fourth horsepower for heavy-duty work, there being less heating of uid from pumping.

Other objects of the invention include the provision of a tracing attachment for machine tools which is greatly improved as to accuracy of the work done and which completely does away with the prior art deciencies of inaccuracies due to oil viscosity variation and overrunning on the part of the tool when an abrupt change is encountered by the tracer in the pattern or templet, the 45 increase in accuracy of the novel apparatus resulting in completely nished work which is made in one pass only of the tool and in which the prior art necessity for returning is completely avoided; the provision of a tracing apparatus as above described including a greatly improved hydraulic circuit resulting in the greater accuracy recited above and including a main valve directly operated by the tracing element, said main valve controlling the pressure at one side of a piston in a power cylinder which moves the tool and the other main partsI of the device, the pressure so controlled being arranged to in turny control a balancing valve, and the balancing valve controlling the admission of pressure to the other side of the piston in the cylinder, so that the advance or retraction of the tracing cutter or tool depends directly on the balancinfy valve, the latter being capable of compartively great changes in the control of the tool upon an extremely small change in the motion of the main valve under direct control of the tracing element. Still further objects of the invention reside in the provision of means for rapid advance, feeding the tool for working, and rapid retraction thereof in the absence of operation of the tracing element; the provision of a pressure control for the system which instantly provides for great increase in pressure when demanded, said pressure control being completely automatically operated; the pro- ,vision of easily operated means by the operator providlCe ing for fast return; the provision for a cycle of rapid advance of the tracing element and the tool to the work, and automatic means for instantaneously changing the hydraulic system to the normal tracing operation from the rapid advance upon contact of the tracing element with the pattern; the provision of automatic and adjustable stops of great accuracy for determining the terminals or limits of motion of the device; and in certain combinations and details of the hydraulic system with the tracing attachment as will appear more fully hereinafter.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings, in which Fig. 1 is a plan view, partly in section, of the novel tracer unit in position on an engine lathe;

Fig. 2 is a slightly enlarged view in elevation of the tracer unit, looking in the direction of arrow 2 in Fig. l but showing certain of the parts in a different position;

Fig. 3 is an enlarged section on line 3 3 of Fig. l;

Fig. 4 is a section on line 4 4 of Fig. 3;

Fig. 5 is a vertical section on line 5 5 of Fig. 4;

Figs. 6 and 7 are diagrammatic representations of the positions of the manual control;

Fig. 8 is an enlarged elevation, looking in the direc tion of arrow S in Fig. 1, part in section;

Fig. 9 is an enlarged section on line 9 9 of Fig. 8;

Fig. l0 is an enlarged section on line .lll-10 of Fig. l;

Fig. l1 is a section on line 11 11 of Fig. 3, certain parts being omitted;

Figs. l2 to 15 are sections on the corresponding lines of Fig. l1;

Fig. 16 is an elevation on a reduced scale with parts in section,( looking in the direction of arrow 16 in Fig. 11;

Fig. 17 is a slightly enlarged section on line 17-17 of Fig. l2;

Fig. 18 is a section on line 18-18 of Fig. 17;

Fig. 19 is an enlarged section showing the main valve in tool feeding position, certain parts being omitted;

Fig. 20 is a similar view showing rapid return;

Fig. 2l is a similar View showing rapid advance;

Fig. 22 is a similar view showing the tracing position;

Fig. 23 is a diagram showing the hydraulic system in tracing position;

Figs. 24 and 25 show representations of different forms of work which may be accurately copied by the tracer of this invention; and

Fig. 26 is a section on line 26-26 of Fig. 6.

Referring now to Figs. l and 2, the present invention is shown as applied to the ways of a conventional engine lathe. These ways are indicated at l0; the tail-stock is generally indicated at 12, the headstock at 14, and the work-driving dog at 16, the work being indicated generally by the character W. This lathe of course is provided with the usual cross-slide and on this cross-slide the unit or apparatus comprising the present invention is removably mounted by bolts or the like conventional fastening devices. By this means, the new unit may be given all the usual motions of the cross-slide.

At the back of the lathe, the same may be provided with removable template brackets 1S which provide centers 20 to clamp a template or pattern 22 in operative position for cooperating with the tracing attachment. These template brackets are provided with clamps, etc. for the centers, and also they may be mounted on a rail 24 detachably applied to the machine base for the purpose.

The unit comprises a tool slide base indicated at 26 and this base may be indexed upon the cross-slide p l indicatedl at 28 as is well-known in the prior art, so

as to provide for different degrees of angularity of adjustment `thereof with -respect to the Work and the tracing element.

Rectilinearly slidably mounted on the tool slide base 26, there is a tool slide 30, and this tool slide may be said to mount substantially'allfofthe.tracer and tracer cutter constructions, includingl the :hydraulicsystem and the automotivegl-forces therefor. To this end, there is provided a housingor the 4'like generally indicatedv at 32 and the main part of the hydraulic system may be located therein. To this housing, there is secured the oil sump, etc. 34 and the pump and the motor bracket, the motor being shown at M and being mounted directly thereon, so that the entire pump, hydraulic system and motor is a single unit, all mounted` on the toolslide for movement therewith under control ofthe :tracing element.

The tracing element isA indicated by the reference numeral 38, and it is located in a tracing arm 40 which providesra housing therefor. The details of the tracing element are best shown in Fig. 3. The tracing element comprises a replaceable tip located in the end of a rod 42, which rod extends generally through the tracing arm 40and terminates in a screw-threaded portion 44 at the rear end thereof.

The tracer rod 42 may be provided with a iiat 43 against which bears one of a pair of adjustable ballbearing rollers 45. This prevents the rod from turning and it is backed up by similar but fixed ball-bearing rollers 47 at the opposite side thereof. The rollers 45 may be mounted on eccentric centers to adjust their position in and out laterally relative to the rod 42 in order to provide an accurate sliding guide means therefor, and set screws 49 are used to hold the adjustments.

The tracing arm 40 is provided with an aperature therein as at 46 and in this aperture there is located an accurate adjusting nut 4S which by means of an interiorly-threaded sleeve 50 in mesh with the threaded portion of rod 42, may be utilized to extremely accurately adjust the position of the tip of the tracing eleL ment SS-with respect to the pattern22 for a-given=posi tion of the tracing arm. A thumb-nut 52 may be used to lock the adjustment and micrometer indicating means are provided for the convenience of theoperator of the machine.

The tracing arm 40 is provided with an interior* enlarged chamber at 54 containing a coil spring 56, said coil spring nding a reaction point at one end of the chamber 54 and at the other end upon a shoulder 55 formed in an enlargement 60 attached to the rod 42. The enlargement 60 is in the form of a sleeve which axially enters andis located within the nut 48. The function of the spring 56 is to continuously press the tracing element to the right, as for instance in Fig. 3, so `that a hub 62 at the center of the nut 48 is constantly in engagement with axially movable pin 64, this pin translating the axial motion of rod 42 within the housing 40 to a main piston-type valve which is indicated at 66. This valve is provided with landsand grooves and is'reciprocable in nature.

The valve 66 is provided with an axially-extending stem68 (see also Fig. l1) surrounded by a coil spring 70 held by a removable nut 72 located at the rear end of the tracer arm housing 40. The spring 70 is stronger than its opposing spring S6 and as an illustration spring 56v may be a two-pound spring and spring 70 as a fourpound spring, so that the valve is normally held firmly against the thrust of the pattern. This provides for an exact sweep or passage otthe tracer'point 3S overtthe pattern, as well as providing for relative axial motion between the tracing rod 42 land the valve 66 relative to the valve housing 74, to provide the variation in pressure kto .actuate the apparatus to displace the slide 30.

A' barrel or the like in the form of a sleeve at 76 surrounds the rod 68 and part of the spring 70. This barrel or sleeve is provided with lateral depressions or notches therein which accommodate the arms 78 ots. yoke 80 as shown in Figs.I 3, 6 and 7, the sleeve 76 has three positions of adjustment as provided for by a handle 82 and shaft 84, the latter rocking under inuence of the handle so that the arms 78 contact the sides of the notches at;94- to move the sleeve. The handle is exposed at the side of the tracing arm housing for convenience of manipulation by the operator and provides manually-controlled rapid advance ,or` rapid retractionof the unibas wellas the centralpositon for the tracing action of the device.

As seen in Figs. 3, 6 and 7, the yoke 80 is provided withV a holding notch 86'which` engages av pointed` end 88 on a latchingslide90held in its uppermost position by the spring 92. In the position shown in Fig. 3, the device is in the tracing position for normal operation', in the position of Fig. 6 the valve parts will be held in position for rapid'advance, and'in-the-positionof Fig. 7 thelvalve 66 will be held in a.: position for-rapidrretraction; It is to be noted that the arms 78 do not contact the sides of the depressions '94in Figs. `6"and `7, when the device is in the Fig. 3^ position, vi;e;, in the tracing position, so that the tracing-rod and valve 66 may move slightly to carry out the tracing operation, and'so that no interference is encountered with' respect to theyokefby reason of abrupt vchanges-in the-"pattern, which of course-will becommunicated tothenextending end 63 of the valve 66.- However, with the'valve' 66 in position of rapid advance, the yoke will snap -the valve over to tracing position upon the'tracer element 38 striking the pattern, and this action is automatic.

The pump is generally indicated at 96 in Fig; 3 and may be directly driven by the motor M, being located in its housing 36 and Thereference nume-rais 98 and 99 show returns or drains and the pressure line-is indicated by the reference numeral 160. Some of the piping has been omitted from this figure to provide for clarity of' illustration, but the pressure of thepump lis directed tothe passage T 2 in Fig. 3 and thence proceeds as will be described hereinafter.

Referring now again to Fig. l, there is shown `a traveling restfgenerally'indicated at 102. This rest may be attached to the crossvslide and it travels longitudinally of the lathe by theconventional mechanism provided in engine lathes for this purpose. As best seen in Fig. 8, the traveling rest is positioned upon the-ways 10 `and it includesl a pair of rollers 104 and 106 which ride upon the surface of the work W after the first cut hasbeen madel by a preliminary traveling tool indicated at 108.

The tool 108 is mounted on ar tool-holder 110 -adjusted by means of the screw 112 and is mountedupon member y102 for `translation with the tool rest and cross` slide, but just in advance of the rollers as clearly seenin Fig. 1. By this means, an accurate surface of revolution is provided at 114 for the rest to contact, and this ensures that the work shall be held exactly correctlywth respect to the centers 20 of the pattern-holding mechanism, and this in turn results in accuracy of work performed, permitting high speed feed rates withoutdeection, without the'usual variation caused by the prior-art inaccuracies in holding' between the pattern and the work itself, Each roller 104 and 106 may be provided with adjusting means as shown in Fig. 9, and this may comprise the Ythumb-screw 116 and the lock 118, thethumbscrew traveling an L-shaped slide 119 on which the respective rollers are rotatably mounted.

Figs. 19' to V23` inclusive illustrate theprincipal -parts of the hydraulic system. The motor M drives'the pump 96 providing iluid pressure in the vpipe 100 leadingfto the valve 66 at T 2. 'Thereisa main branch 120 to the valve 66 and this has-a small restricted passage at 122 that leads into the valve housing 74 at a different position.

A passage 124 leads from the valvehousing 74into' the cylinder indicated at 126 at the piston rod side thereof which is indicated at B, this standing for the bottom of the cylinder as respects the piston 128, the other side of which is labeled T which stands for the top of the cylinder.

The cylinder 126 is xed to and moves with the entire unit, the piston 128 being lixed on the rod 130 to a projection or ange 132 at the rear end of the toolslide base 26. This may be accomplished by means of a bolt or the like generally indicated at 134 (Fig. 11). Thus upon pressure at the bottom of the cylinder, the entire sliding tool unit will be retracted, and upon pressure being applied to the top of the cylinder, the tool Will advance.

A passage 138 leads from the left-hand end of the valve housing 74 to the top of the cylinder and is in open communication with the passage labeled TA. Also, there is a passage of a more restricted nature labeled TC (see diagram Fig. 23), and there is another passage 140 which is provided with a feed control needle valve F of conventional type. Passages 138, TC, 140 and 124 are all pressure passages but in certain conditions of valve 66, passage 138 may go directly to the sump labeled S (see Fig. 20).

Passages 124 and 140 communicate and extend to lead linto the bottom of the cylinder B as at 142; adjacent this location, there is a valve generally indicated at G which is normally held closed by the spring 144 but which may be opened to direct the bottom of the cylinder directly to the sump as indicated by the pipe 146.

Also adjacent this point, there is a branch pipe 148 that leads to one end 150 of a valve housing 152 having a piston valve 154 therein. The passage TC also leads into this passage centrally thereof, as also does passage TA in the relationship shown in Fig. 23, and there is a branched passage 156 leading to the sump through the passage 158.

The valve 154 is provided with a spring 160 which constantly tends to move the same to the left. This valve is provided with a center passage 162 by which the passages TC and TA may communicate in varying degrees, depending upon the position of valve piston 154 under iniluence of the spring 160 and the pressure in the passage 148, which pressure tends to move the valve 154 to the right against the spring tension.

The valve 66 is directly connected to the tracer control rod 42 and is provided with the opposing springs above described, these springs being indicated at 56 and 70, for the purpose noted. The valve itself is provided with an annular passage at 164, another at 166, a third at 168, and a fourth at 170, and in addition there is a return to the sump at 172.

The tracing condition will be described first, and this is shown in Fig. 22 wherein the representation of the valve 66 shows the fact that the passages 138 and TA are always in communication, regardless of the position of the valve. The pressure enters the port at 120 and passes into the passage TC, the lines at 138 and TA being cut off both fro-m the sump and from the pressure. However, the branch pipe 122 leads pressure into the valve passage 168; and with the parts in position shown in Fig. 22, the lluid is seen to pass by valve part 174 to the sump as by the passage at 172. The valve part 174 is located between and closely adjacent the two shoulders 176 and 178 in the valve housing, so that a small amount of oil is conducted through the passage 140 past the metering valve F and to the bottom of the cylinder B.

An extremely small change in the position of the valve 66 is sufficient to change this relation. If the valve. 66 be moved very slightly to the right, the small passage between the shoulder 176 and the part of the valve at 174 increases and the passage between. this vsame part of the valve and the shoulder 178 decreases. This action raises the pressure at 140, which means that the pressure is raised in the bottom of the cylinder B, whereupon the cylinder moves to the right an lamount inA ratio to the movement of the valve.

As soon as the cylinder 126 moves to the right, then the valve housing 74, together with the entire slide and all the movable parts, also so moves, returning the shoulders 176 and 178 to original position relative to the valve part 174, whereupon the original pressure situation is re-imposed and the tracing device will be again once more traveling a straight line with the -cross-slide.

When the pressure rises as at 140, it likewise rises in the passage 148 and this moves the valve 154 to the right against the action of the spring 160. When in tracting position, the valve part 153 of valve 154 Was positioned to allow a small passage of iiuid from the passage TC to the passage TA, and thus into the top of the cylinder T, the sump being cut otf, balancing the pressure in the bottom of the cylinder. But when the valve 154 is moved to the right as described, it actually narrows the small aperture existing from passage TC to the valve at 162,

so that the pressure at the top of the cylinder is correspondingly decreased, providing for the action aforesaid. It is to be noted that the size of the openings at 176 and 178 may be on the order of thousandths of an inch, and that extremely small differences will cause the changes described.

If on the other hand, the valve 66 should be moved to the left from the position of Fig. 22, the passage at the shoulder 176 is lessened in extent and that at 17S is increased, thus decreasing the pressure at 140 and at 142 and in the bottom of the cylinder. This action decreases the pressure at 150 with regard to valve 154, and the spring 160 then tends to move valve 154 to the left, making the passage at TC larger, so that the pressure at the passage 162 to passage TC is allowed in increase through valve 66 and passage TA to the top of the cylinder, thus moving the entire apparatus to the left and causing tool 136 to make a deeper cut in the work.

The element G operates to open the bottom of the cylinder to the sump, whereupon pressure at the top of the cylinder will obviously cause the cylinder to be moved very rapidly to the left, relieving the pump of most of the pressure and avoiding heating. As explained above, the handle 82 may be manually operated to achieve instant pressure to move the yoke to accomplish rapid return and rapid advance as desired without relation to the tracer element.

If it is desired to feed the tool without relation to the tracer, the valve 66 is placed in the position shown in Fig. 19 by knob 82. In this case, the passage 140 is open to the sump; the pressure line directly corna municate's with TC; by this means the passage TA is provided with pressure in order to allow the cylinder 126 to move continually to the left without interruption. v

On the rapid return, the passage at 172 is closed. Pressure in the restricted passage 122 communicates directly with the passage 141) and the passage TC is cut oir, there being pressure applied also through the line 124 combined with the pressure in to rapidly withdraw the cylinder to the right in Fig. 23.

In the condition of rapid advance, the passage at 172 is again cut oif as is the passage at 140. The pressure at 120 is open to 138 and TA directly, which causes high pressure at the top of the cylinder, causing the same to move to the left rapidly.

There is provided a shuttle valve D, one side of which is open to passage TA and the other to passage 142, TA and 142 leading to opposite sides vof the piston 128. When excess pressure is called for in either direction, the shuttle valve D will shift, thus applying pressure in the piping 184 which leads to an automatic pressure control deviceC. Excess pressure in the pipe 100 urges the piston in the device C upwardly against its spring C1 so'as to pass such excess pressure to the pipe 186 to the sump by pipe 188, the latter also providing for the surnp return from the branch pipe 15,8. Upon pressure being built up '.7 above the piston. in the automatic .control .(3, this. piston moves downwardly and Yallows buildupof pressure in the pipe 100- and throughoutA the system where. called for, being directed to the side of the ,piston required,.depend ing upon which side ofthe ypistoncalls for theincreased pressure. There is also a maximum pressure valve at E through which the pressure from passage 184 will leak when a certain high predetermined pressure is. reached.

Fig. shows in section a form of automatic control for the valve G. In this case, the tool slide base rear flange 132 is provided with a stop -pin 1963 movable in an adjustable cylinder 191 and backedup by a spring 192. A setscrew 194 holds the cylinder in adjusted position. 'Ille too-l slide housing carrieswithit. astop rod 193, aligned with the member 19.0, andbacked up by the. spring 144 whichisweaker. than spring.192. The stop pinllll will giveuponcontact therewithin order to open the valve as. at 196 corresponding to the. valve G in Eig. 23 inorder to causethe uidto beconducted di,- rectly to the drain upon arrival of the .tool-slide at4 its rearwardmost position.

Also, the tool slide rear flange 132 carriesa micrometer screw adjustment generally .indicated at 198controlling the screw-rod 200. This screw-rod hasan adjusting nut and lock-nut 202 for providing a limiting stop in the forwarddirection of the. toolslide 30. By the-,use of the micrometer head 19.8,a-very exact position of the end of the travel of the tool-slidev is. provided. The motor is provided with an.on and off switch 204 and apropriate overload protection is provided withv this switch.

Referring to Fig. l2, there is provided an adjustable control for converting the travel of. thetoolslide from rapid traverse to a feed position and` this comprises a pin 2% mounted in the tool-slide base rear ange132, there being mountedthereon a forwardly-extending rod 208, the main portion of which islocated in the housing 32. This rod is provided with an adjustable stop generally indicated at Zit), the detailsv of which are illustrated in Figs. 17 and 18. This stop may be adjusted relatively to rod 208 by meansof the spring and ballclutch therein generally indicated at 212, the spring wedging the ball into gripping relationship upon1being released by a sleeve 214 to position the stop 210 at a desired longitudinal position on rod 208.

Cooperating with the stop there is aplunger rod 216 which is axially movable. by the inclined .surface 218 of the adjustable stop in order to rock an element 220, and in turn rocking element 222 by means of a. rod 224. Upon rocking of element 222, a shaft 22.6 is oscillated, rinturn oscillating a rod 228 which isiconnectedto the shaft 34 at an offset locationas at 230. As described above, shaft S4 controls valve 66, see Fig. 7.

By this means, the device is automatically thrust into feed position at a certainadjusted location, i. e.,.at.the ond of the adjusted rapidtraverse stroke and thereafter the device operates in the feed position .of the main valve.

Thetool post itself as illustrated generally at 232 is the same construction as illustrated in my copending application Serial No. 5.4159liiled October 20, 1955, and with the constructionrecited aboveextremely accurate workv is performednot only with` the more usual typesv of templates as illustratedin Fig. 1, but with the more difficult types of work to perform as illustrated in Figs. 24 and 25. It will. be seen from these diagrams that the present tracer is capable of performing extremely accurate cuts on the concave surfaces shown therein and the interior surfaces as at 236 and 238 respectively.

It willV be seen from thc-above that thistinventioncan ries out all ofthe objectsstated.v above, andlthat aswell as providing extreme -accuracy, theunit.is able toprovide the same in many different typesof workv atlower4 cost due to. simplicity of constructionand to. the factthatthe hydraulic system allows for a ymuch smaller motor` to be used to provide the uidpressure necessary;l and further'- more such` motor is mounted in a unitary manner with the rest ofthe device so that all that is necessary to do to convert any` conventionallengine.lathe into a tracing lathe is to setup thev template holding .centers and to mount the unitv of this invention on the cross-slide of the lathe, plugging the motor into an electric outlet. The device is extremely light-weight, economic, and small compared to devices of the prior art for the same purpose; and it is easily attached and removed from the lathe without the necessity of. large motors, pumps and complicated iiuid pressure systems which require support at remote locations at the `back of the lathe, on the oor, etc.

The tracer point pressure is very light and even wooden templates can be used for speed and economy; use of the attachment is not limited to production work, as any piece canbe used for a template to make a replacement partusing the ymicrometer nut on the tracing arm to compensate for wear or for grinding surfaces; thread chasing may be accomplished; and the invention provides for a power` feed compound tool slide with rapid traverse and hydrauliofeed, with an adjustable stop for shifting from rapid traverse to feed.

Having ,thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I' claim is:

l'. A tracing apparatus for machine tools comprising a tool, a relativelymovable piston and cylinder to move the tool, a tracer for movement under influence of a pattern, a main valve actuated by the tracer, a balancing valve hydraulically actuated by the main valve, a source of hydraulic pressure and a hydraulic circuit for the cylinder and valves, the balancing valve being directly connected to the cylinder at one side of the piston, the main valve providing hydraulic .pressure for control by the balancing valve for the one side of the piston, said main valve` being connected directly to the other side of the piston and to one side of the balancing valve to move the latter according to the pressure at said other piston side. as controlled by the main valve.

2. A tracing apparatus for machine tools comprising atool slide, atool thereon, a cylinder and piston to move the tool slide, a tracer formovement under inuence of a pattern, and a hydraulic system for moving the tool slide in accordance with the motion of the tracer, said system comprising a balancing valve for Variably admitting' fluid under pressure to the cylinder at one side of the piston, a main valve Vfor variably admitting iiuid under pressure directly to the other side of the piston, means to control the position of the first valve under iniiuence of thepressure at said other side of the piston, the position ofthe toolbeing controlled by the pressure at the other side of Ythe pistonandvthis pressure being controlled by the main valve, said tracer being connected to operate the main valve.

3. T he` tracing apparatus of claim 2 including means to communicate increased pressure at the other side of the piston tothe rst valve to move the latter, and means intherst valve to tend to close oli pressure to the one sidejof the piston upon such movement.

4. The tracing apparatus of claim 2 including means tocommunicate increased pressure at the other side of the piston'totheiirst valve to move the latter, and means in the first valve to tend to close ott pressure to the one side. of thel piston upon such movement, the main valve moving withthe tool slide and tending to move to original relationship relative to the tracer and main valve, to restore original pressure to the other side of the piston, and means to movfe the first valve to original position upon reduction ofipressure'thereon.

V5 Tracing apparatus comprising a base, a tool slide thereon, a tracer element,a main valve operated by the tracer element, a source of fluid pressure, a balancing valvesaid main valve supplying iluid pressure to the balancing Yvalve, a cylinder andl piston for moving the tool slide in accordance with the tracer element, said main valve supplying iluid pressure to one side of the piston and to one side of the balancing valve, the latter supplying the iiuid pressure from the main valve to the other side of the piston and being moved to supply alternatively less or more uid according to the respective rise and fall of pressure at the one side of the piston as determined by the relative position of the tracer element and the main valve.

6. The tracing apparatus of claim 5 including means to control the pressure of the fluid, and means to operate the pressure controlling7 means to raise the pressure upon relatively large imbalance of pressure between the two sides of the piston.

7. The tracing apparatus of claim 5 including means to Icontrol the pressure of rthe fluid; and means to operate the pressure controlling means to raise the pressure upon relatively 4large imbalance of pressure between the twosides of the piston, said last-named means including a shuttle valve located between the two sides of the piston the pressure controlling means to raise the pressure upon relatively large imbalance of pressure between the tWo sides of the piston, said last-named means including a shuttle valve located between the two sides of the piston and alternatively connecting the respective piston side uid pressure with the pressure controlling means, and a high pressure control valve associated with the shuttle valve and regulating the maximum pressure of the fluid system.

9. The combination of an engine lathe having ways and a cross-slide with a tool base to be removably secured to the cross-slide, a motor, a uid pump driven thereby, a main valve, a balancing valve, a tracer element actuating the main valve, a cylinder and piston, a tool reciprocated thereby, the main valve varying the pressure at one side of the piston and the balancing valve varying the pressure at the other side of the piston in inverse ratio thereto, said balancing valve being connected to the said one side of the piston and being variably actuated thereby.

10. A tracer apparatus comprising a base adapted to be relatively traveled along a piece of work to be operated upon, a tool slide on the base to be reciprocatively actuated in and out relative to the work-piece as the base travels, the motion of the tool slide being under the control of a pattern for this purpose, a tool on the tool slide, a tracer arm movable with the tool slide, a movable tracer element on the tracer arm, a main piston valve movable fby the tracer element relative to the tool slide, a source of uid pressure leading to the main valve, a power cylinder and piston for moving the tool slide in accordance with momentary changes of position of the main valve relative to the tool slide, said main valve including means to vary the pressure in the cylinder at one side of the piston upon the occurrence of such momentary changes to cause motion of the tool slide to return the same and main valve to original relationship, a balancing piston valve having one side of its piston open to the said power cylinder at the said one side thereof for movement of the balancing valve by the variation in pressures, means yieldably opposing the pressure on the balancing valve, means leading uid pressure to the balancing Valve to be controlled thereby and leading from the balancing valve to the power cylinder at the other side of the piston thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,905,132 Bishop Apr. 25, 1933 1,970,181 Monroe Aug. 14, 1934 2,069,426 Smith Feb. 2, 1937 2,239,413 Dewey Apr. 22, 1941 2,464,626 Waterson Mar. 15, 1949 2,526,487 Kurzweil Oct. 17, 1950 2,603,117 Turchan July 15, 1952 2,695,543 Von Zelewsky Nov. 30, 1954 2,729,130 Walker Jan. 3, 1956 FOREIGN PATENTS 684,809 Great Britain Dec. 24, 1952 733,042 France Sept. 29, 1932 738,446 Great Britain Oct. 12, 1953 

